Rotary solenoid



Aug. 24, 1965 E. ELLNER ROTARY SOLENOID 2 Sheets-Sheet 1 Filed May 8, 1965 BY WMQWJ ATTORNEYS Aug. 24, 1965 E. ELLNER ROTARY SOLENOID 2 Sheets-Sheet 2 Filed May 8, 1963 FIG. 3

FIG. 4

INVENTOR. EDWI N E LLN ER 777M2 4 fla 4 ATTORNEY United States Patent O 3,262,350 ROTARY SOLENOID Edwin Ellner, Oxford, Conn, assignor to Consolidated Electronics Industries Corp, Waterbury, Conn, a corporation of Delaware Filed May 8, 1963, Ser. No. 278,816 12 Claims. (Cl. 31037) The present invention relates to rotary solenoids, a d more particularly to an improved closing-air-gap type of DC. rotary solenoid having a pair of electromagnetic coils and a permanently magnetized armature.

It is a general object of the present invention to provide an efiicient rotary solenoid having a long throw and a relatively high torque. Another object is to provide a rotary solenoid which has a low wattage requirement per unit of torque. A corollary object is to provide a solenoid for use in low-power, continuous rating applications. The rotary solenoid of the invention provides the above-mentioned, desired operating characteristics, and has a utility in numerous applications, an advantageous one of which is as a low-power, driving means for rotary switches, encoders and the like.

A further object of the invention is the provision of means to insure a repeatedly uniform and reliable mechanical output from a coupled rotary solenoid and ratchet and pawl mechanism. Accordingly, in the following description, the new and improved rotary solenoid appropriately includes a rotary encoding switch coupled therewith through a ratchet and pawl mechanism.

Other objects and advantages will be apparent from the following detailed description of a preferred embodiment of the new mechanism, and from the accompanying drawings, in which:

FIG. 1 is a cross-sectional view of a rotary solenoid, embodying the principles of the present invention, coupled by a novel pawl and ratchet mechanism to a rotary encoding switch to form a rotary switch unit;

FIG. 2 is an enlarged fragmentary cross-sectional view showing the mounting on independent shafts of the solenoid elements and ratchet elements of the mechanism of FIG. 1;

FIGS. 3 and 4 are cross-sectional views of the mechanism of FIG. 1 taken along lines 33 and 44, respectively, thereof; and

FIG. 5 is an enlarged detail view showing the tapered air gap between the armature and pole piece of the rotary solenoid of FIG. 1.

With reference to FIG. 1 of the drawings, the rotary solenoid assembly of the present invention, indicated generally at 10, is shown coupled through a ratchet and pawl mechanism 11 to a multi-position, rotary, printed encoding switch 12. A tubular housing 13 generally encloses the solenoid and switch assembly and is closed off at one end by an end plate 14 to form a self-contained rotary switch unit. For the purpose of clear description only and not in any limiting sense, that end of the unit closed by the plate 14 will be designated and referred to as the rear or back end, while the other end will be designated and referred to as the front end.

Four main support posts 16 extend longitudinally from the front end of the housing 13 to the end plate 14 and are secured therebetween by screws 16'. A pair of supporting plates 18, 19 and a brush board 17 are carried in predetermined spaced relation within the housing by the main support posts 16.

In accordance with one aspect of the invention, the rotary solenoid assembly includes a spaced pair of electromagnetic coils 20', 21 wound about iron cores 22, 23, respectively, and mounted in an electromagnetic flux linking relation with a pair of P l-shaped pole pieces 24, 25. As best shown in FIG. 4, flanges 34, 35 extend outward Patented Aug. 24, 1955 from the body portions of the pole pieces 24, 25 and twin coils 2d, 21 are secured by screws 26 between the flanges. The body portions of the pole pieces are p ovided with facing arcuate recesses 24a, 25a forming pole faces of predetermined, advantageous form, to be described in more detail.

The assembled electromagnetic coils 2d, 21 and pole pieces 24, 25 form the stator element of the new and improved rotary solenoid, which stator element is secured to the plate 13 by a series of nuts 64 and bolts 65. Accurate positioning of the pole pieces 2 25 is insured by alignment pins 65, which locate the pole pieces with respect to the supporting plate 18.

The armature of the rotary solenoid 10 is an elongate, frusto-cylindrical permanent magnet 27 having parallel sides 28 and arcuate north and south pole tips 29, 3d. Advantageously, the magnet is fabricated from a magnetically hard material such as Alnico No. 5, and the grain direction of the magnetic material is arranged to be substantially parallel (:5") with the longitudinal sides 23, from pole tip to pole tip as shown in FIG. 5. A rotor shaft 31, rotatably supported at its rear end in a bearing 32, mounted in the plate 18, is secured to the magnet by means of a core 27' of a material such as Cerro-Met. Support of the front or free end of the shaft 31 is provided by a solenoid end plate 33, which is secured, along with the pole pieces 24, 25, by the nuts 64 and bolts 65. The combination of the rotatably supported shaft 31 and the elongate permanent magnet 27 forms the rotor element of the solenoid.

As shown in FIG. 2, the rear free end of the rotor shaft 31 projects through the support plate 13 and mounts, by means of a hub 47 and pin 48, a pawl arm 36 having a driving pawl 37 pivotally mounted thereto. Biasing of the pawl arm 36 toward an upper stop 39 is provided by a spring 42 connected between a stud 43 on the plate 18 and an aperture 36' in the pawl arm. The driving pawl 37, itself, is biased by a spring 38, as shown in FIGS. 1 and 3, and is pivotable about a mounting stud 37 The front face of the plate 13 mounts a pair of stops 39, 40, which limit the travel of the pawl arm 36. As shown in FIG. 3, the lower stop has an adjustable eccentric stop 41 rotatably mounted on a pin 49a. projecting from the stop 40.

The solenoid sub-assembly and the driving pawl, constitute the driving means for the rotary switch assembly. The driven means, a printed circuit disc 12, is fixed to an output shaft 44 by means of a flared hub 45 and set screw 46, as shown in detail in FIG. 2. The shaft 44 is supported at its outer end by a bearing 5d, carried by the end plate 14, and at its inner end by a bearing 51, carried by the plate 19.

Rotary motion of the rotor shaft 31 is transmitted to the output shaft 44 through the pawl and ratchet coupling 11. This driving coupling is completed by a ratchet wheel 52 held by a force fit to the free end of the output shaft, which end projects beyond the plate 19 as clearly illustrated in FIG. 2. A second pawl 53 is pivotally mounted on the front face of the plate 1? on a stud 54 and is biased by a spring 55 to insure positive engagement with the teeth of the ratchet wheel 52. The pawl 53 serves to prevent reverse rotation of the ratchet wheel 52 during reverse or retracting movements of the pawl arm 35.

In accordance with one of the specific aspects of the invention, overrun of the ratchet wheel 52 is prevented by means of the adjustable eccentric stop 41, which is held by a set screw 41a in a predetermined position as shown in FIG. 3. In its properly adjusted position, the stop 41 maintains a slight clearance with respect to the driving pawl 37 when the arm 36 is engaged by the stop 4%. However, if the ratchet wheel 52 tends to overrun,

2.3 by reason of excessive inertia, the forward motion of the wheel will urge the pawl 37 outward and into engagement with the eccentric stop 41. This prevents the pawl arm from swinging outward far enough to clear the next ratchet tooth and thereby positively prevents overrun of the wheel.

The brush board 17 carries a plurality of resilient, electrically conductive brushes 56, which are adapted to cooperate conventionally with the coded printed circuit disc 12 to make and break electrical circuits as the disc is rotated. Suitable electrical leads 57, 60 (shown in FIG. 4) are adapted to connect the brushes and the coils 20, 21 with an array of terminals 58 in a header 5@ located in the front wall of the housing 13.

In accordance with one aspect of the invention and with reference to FIGS. 4 and 5, the air-gap between the convex armature pole tips 29, 3t and concave stator pole faces 24a, 25a is of predetermined tapered configuration, diminishing in width toward the neutral position. To this end, the radius of the stator pole faces 24a, 25a is greater by a predetermined amount than the radius of the pole tips 29, 30 of the armature 2'7, and the centers of curvature of the pole faces 24a, 250 are displaced from the center of curvature of the armature-tips to either side of the axis of symmetry of the solenoid. Thus, the pole faces 24a,125a have a non-circular profile with respect to the solenoid axis of symmetry, while the pole tips define a generally circular profile with respect to the same axis of symmetry. In accordance with the invention, this geometrical relationship defines a tapered gap between the rotor pole tips 29, 30 and the pole faces 24a, 25a, with a minimum gap A occurring at the central portions of the stator pole faces 24a, 25a and a maximum gap B at the extremities of the stator pole faces.

By way of specific example, in a typical solenoid assembly according to the invention, in which the radius of the armature magnet in 0.375 inch, the stator pole faces advantageously have a radius of 0.395 inch, and a center of curvature C displaced about 0.015 inch beyond the rotational axis D of the armature, along the axis of symmetry indicated at X in FIG. 5. This arrangement provides for a theoretical minimum air gap, along the (neutral) axis of symmetry, of about 0.005 inch increasing gradually moving away from the neutral axis.

With the stator tin-energized, the armature 27 is arranged to be in the rest position, shown in phantom in FIG. 4, by proper rotary orientation of the armature 27, pawl arm 36 and stop 39. In rest position the armature and stator are oriented to form a generally maximum air gap there'oetween (e.g., 0.020 inch, theoretical maximum in the typical assembly described above).

Advantageously, orientation of the armature magnet and pawl bar is such that'the armature magnet has an operating motion of about 15 rotation on either side of an axis at right angles to the neutral axis of the electromagnetic poles, providing a full stroke of about 30.

In accordance with the invention, the two coils of the stator magnet are arranged for connection to a DC.

by the flanged stator poles, directing the flux inward I from both coils 20, 21 and tending to create a flux concentration along the neutral axis X, the actual flux path being distorted somewhat by the presence of the armature magnet 27.

When the permanently magnetized armature 27 is in its rest position, the north and south poles of the armature lie under the north and south stator poles, respectively. Accordingly, when the coils 20, 21 are energized initially, the armature magnet is acted upon primarily by repelling forces, changing to primarily attracting forces as the armature magnet swings through its vertical (as viewed in FIG. 4) axis and is drawn to its stop position illustrated in full lines in FIG. 4.

Particularly desirable and efficient flux formations and concentrations are achieved through the cooperative relationship of a symmetrical, two-coil stator configuration, tapered cylindrical air gap, and a permanently magnetized armature element oriented about an axis normal to the neutral axis of the stator.

The total rotation of the armature 27 is limited by the stops 39, 40, which limits the travel of the pawl arm 36, fixed to the rotary shaft 31. Upon de-energization of the stator, the pawl arm 36 will be urged by the spring 42 in a counterclockwise direction into the rest position against the upper stop 39 to return the armature to its rest position shown in phantom in FIG. 4.

Each clockwise advance of the pawl arm, a result of the energizing of the armature with a pulse of DC, causes the drive pawl 37 to engage the ratchet wheel 52 and angularly displace it a predetermined amount, determined by the spacing of the stops 39, 40. The ratchet wheel 52 :is prevented from counterclockwise or reversed movement by the anti-reverse pawl 53.

Prevention of angular displacement of the ratchet Wheel in excess of the desired amount is accomplished by the adjustable eccentric stop 41, which stop acts to revent the disengagement of the drive pawl 37 from the ratchet Wheel 52 when the pawl arm 36 is against the stop 40. Each successive energization of the rotary solenoid causes the printed circuit 12 to index with the ratchet wheel the predetermined angular amount to a new switching position. At each new position, the printed circuit will complete an electrical circuit between predetermined ones of the brushes 56 to accomplish a desired switching action.

The rotary solenoid of the present invention, with its twin-coil design, permanent magnet armature and tapered air gap, provides a new and improved type of rotary solenoid requiring minimum wattage per unit of torque produced. In comparison with conventional, inductiontype solenoids having soft iron armatures, the new rotary solenoid, with a permanently magnetized armature, has a longer throw and higher torque. Moreover, the balanced, twin-coil design, as employed in the combination, adds significantly to the overall operating efiiciency and reliability of the unit.

While the present invention has been described with respect to a specific, preferred embodiment by way of illustration only, the scope of the invention is to be limited only as set forth hereinafter in the appended claims.

' V I claim:

1. A rotary solenoid, comprising (a) a pair of spaced pole pieces having concave pole faces and being supported in a fixed relation,

(b) a permanently magnetized, elongate rotor element having a pair of convex pole tips of opposite magnetic polarity,

(c) a rotatable shaft supporting said rotor element for rotation between said concave pole faces,

(d) said convex pole tips and said concave pole faces defining a tapered air gap therebetween,

(c) said air gap being of minimal width opposite the central portions of said concave faces and said air gap being of maximum width opposite the extreme portions of said concave faces, and

(f) a pair of electromagnetic coils disposed in flux linking relation with said pole pieces and adapted to be energized by a source of DC. to magnetize oppositely said pole pieces.

2. A rotary solenoid according to claim 1, in which (a) each of said pole pieces includes a body portion and a flange extending outward from said body portion,

(b) said body portions define said concave pole faces,

and

(c) said flanges are secured to said coils.

3. A rotary solenoid according to claim ll, in which (a) said convex rotor pole tips have a curvature greater than the curvature of said concave pole faces with respect to the axis of rotation of said rotor shaft.

4. A rotary solenoid according to claim 1, in which (a) said rotor pole tips underlie the extremities of said pole faces,

('0) said electromagnetic coil means are adapted to produce a maximum concentration of flux at the centers of said pole faces,

(c) whereby said pole tips tend to align themselves inwardly of said extremities toward said centers of said pole faces.

5. A rotary solenoid, comprising (a) a stator element,

(b) electromagnetic coil means adapted, upon energization with a source of DC, to polarize said stator element,

(c) a rotor element,

((1) a rotor shaft carrying said rotor element,

(e) said rotor element being rotated in a first predetermined direction by said stator element,

(f) a driving arm fixed to said rotor shaft,

(g) a driving pawl means carried by said arm,

(h) rotatable output shaft means,

(i) a ratchet wheel fixedly mounted to said output shaft means for rotation therewith and adapted to be indexed by said drive pawl means,

(l) first stop. means adapted to limit the rotation of said driving arm in said first predetermined direction,

(1;) second stop means adapted to limit the rotation of said driving arm in a second predetermined direction,

(1) spring means urging said driving arm toward said second stop means, and

(m) auxiliary stop means adapted to limit the motion of said drive pawl means with respect to said first stop means.

(i. A rotary solenoid according to claim 5, in which (a) said auxiliary stop means is adjustably mounted on said first stop means.

7. A rotary solenoid according to claim 6, in which (a) said second stop means includes a projecting pin means,

() said auxiliary stop means is of substantially cylindrical configuration,

(c) said auxiliary stop means is rotatably mounted to said pin means about an axis offset from its axis of symmetry,

(d) whereby said auxiliary stop means is eccentrically adjustable with respect to said second stop means.

8. A rotary solenoid, comprising (a) frame means,

(b) a pair of spaced pole pieces having concave pole faces and being supported in a fixed relation with said frame means.

(c) a permanently magnetized, elongate rotor element having a pair of convex pole tips of opposite magnetic polarity,

(d) a rotatable shaft supporting said rotor element for rotation between said concave pole faces,

(e) said convex pole tips and said concave pole faces defining a generally cylindrical tapered air gap therebetween having minimum width opposite the center portions of said pole faces,

(f) a pair of electromagnetic coils disposed in flux linking relation with said pole pieces and adapted to be energized by a pulse of DC. to magnetize oppositely said pole pieces.

9. A rotary solenoid according to claim 8, which ineludes (a) biasing means normally urging said rotor element into a position of generally maximum air gap,

(b) said biasing means being suiiiciently weak to be overcome by the magnetization of the said pole pieces.

16. A rotary solenoid, comprising (a) a pair of stator pole pieces having concave pole faces of predetermined radius,

(b) means mounting said pole pieces in predetermined spaced relation on opposite sides of a predetermined rotational axis,

(c) said predetermined radius being greater than the spacing of said pole faces from said rotational axis,

(d) a pair of electromagnetic coils mounted on opposite sides of said pole pieces and extending from one pole piece to the other,

(e) said coils being energizable by a DC. source to oppositely polarize said pole pieces, and

(f) a permanently magnetized rotor element mounted for rotation about said axis and within the embrace of said pole pieces,

(g) said rotor element being oppositely polarized at its opposite ends.

Ill. A rotary solenoid according to claim it), in which (a) spring means are connected to said rotor element to urge it into a predetermined starting position in which the permanently magnetized poles of said rotor each generally underlie pole pieces which are magnetized by said D.C. source to the same polarity as said rotor poles.

12. A rotary solenoid according to claim llll, in which (a) each of said rotor poles underlies portions of both of said pole pieces in said predetermined starting position,

(b) said rotor poles underlying greater surface portions of the pole pieces which are magnetized to the same polarity than the pole pieces which are magnetized to the opposite polarity.

No references cited.

MILTON O. HIRSHFIELD, Primary Examiner. 

1. A ROTARY SOLENOID, COMPRISING (A) A PAIR OF SPACED POLE PIECES HAVING CONCAVE POLE FACES AND BEING SUPPORTED IN A FIXED RELATION, (B) A PERMANENTLY MAGNETIZED, ELONGATE ROTOR ELEMENT HAVING A PAIR OF CONVEX POLE TIPS OF OPPOSITE MAGNETIC POLARITY, (C) A ROTATABLE SHAFT SUPPORTING SAID ROTOR ELEMENT FOR ROTATION BETWEEN SAID CONCAVE POLE FACES, (D) SAID CONVEX POLE TIPS AND SAID CONCAVE POEL FACES DEFINING A TAPERED AIR GAP THEREBETWEEN, (E) SAID AIR GAP BEING OF MINIMAL WIDTH OPPOSITE THE CENTRAL PORTIONS OF SAID CONCAVE FACES AND SAID AIR GAP BEING OF MAXIMUM WIDTH OPPOSITE THE EXTREME PORTIONS OF SAID CONCAVE FACES, AND (F) A PAIR OF ELECTROMAGNETIC COILS DISPOSED IN FLUX LINKING RELATION WITH SAID POLE PIECES AND ADAPTED TO BE ENERGIZED BY A SOURCE OF D.C. TO MAGNETIZE OPPOSITELY SAID POLE PIECES. 